The present invention relates to wound management and, more particularly to novel wound dressings for large scale production and subsequent sale, which invention obviates certain deficiencies to be discussed hereinafter in current industrial protocol for manufacturing dressings for treatment of wounds, burns, incisions and the like.
Irrespective of the dressing design and manner of making, it is most desirable in wound care management to provide a dressing which will maintain the desired moist environment promoting healing while at the same time preventing scab formation; and also permitting removal of wound fluid which can build up a pressure bubble beneath the dressing, thereby undermining the adhesive seal adhering the dressing to the skin and thereby increasing the possibility of the wound being contacted by ambient contaminants, including, of course, microorganisms which can cause infection.
Seemingly, these two objectives are often at cross-purposes so that one of the two objectives is accomplished to the detriment of the other. Yet, dressings alleging to fulfill both objectives have heretofore been described in the patent literature.
As stated in Col. 1 of Webster, it has long been a recognized problem that dressings are inclined to suffer from either or both of the disadvantages that they sometimes tend to float away from a wound or else they sometimes tend adhere to the wound surface.
The former of these disadvantages generally occurs when the wound is one that produces large volumes of exudate. Generally, the method of overcoming this problem is to provide the dressing with holes so that exudate can escape and the dressing remain in contact with the wound. Certain attempts to achieve this end are said to be disclosed in UK Pat. Nos. 778,813; 1,298,011; and 1,408,345; and patent application Ser. Nos. 2,061,732 and 2,074,029. One successful dressing is Melolin(trademark) (Smith and Nephew Ltd.) which comprises a perforated synthetic polymer film and an absorbent cellulosic pad. The perforated film is placed next to the exuding wound so that exudate can pass through the perforations to the overlying absorbent pad where it is absorbed. A later suggestion has been to use a perforated polytetrafluoroethylene film in an effort to minimize the adherence of the dressing to the wound.
Alternatively, dressings have been suggested which comprise a thin hydrophobic film laminated to a fibrous absorbent layer. The film contains a number of apertures in the form of slits. Such dressings are described, for example, in British Pat. Nos. 815,121 and 1,163,452 and U.S. Pat. No. 3,602,220. However, dressings of that type have not been found to be satisfactory because either the slits do not open or they do not open wide enough to allow passage of exudate through the film to the absorbent.
The second of the aforementioned disadvantages generally occurs when the wound has dried out due to lack of production of exudate to maintain a moist environment. Generally, the method of overcoming this problem is to provide the dressing with a continuous layer which retards the rate of loss of water. One effective method of achieving this end is described in British Pat. No. 1,280,631.
The Webster patent then states that none of the known methods are free of disadvantages, since what may be an excellent dressing for one kind of wound will be unsuitable for many other wounds, since wounds differ greatly in their output of exudate. Accordingly, says the patentee, it has now been realized that, not only is there a need for a dressing that is more suitable for use on a number of different types of wounds, there is also a need for a dressing which can better cope with the variation in rate of exudate production from the wound,
According to the Webster invention, a dressing has now been discovered which allows passage of a greater amount of exudate from a wound producing larger amounts of exudate, but which allows the wound to remain moist when it produces only smaller amounts of exudate, so that the dressing does not float away from an overly moist surface, nor does it have a tendency to adhere to a dry wound. The new dressing is also said to aid in the re-epithelialisation of the wound.
Accordingly, the patented invention is said to provide a dressing comprising a conformable film with apertures therethrough characterized in that the film comprises a first layer laminated to a second layer, the first layer comprising a material which swells when in contact with water and the second layer comprising a material which when in contact with water does not swell or swells less than the first layer. The apertures are enlarged when in use on a wet surface and otherwise not enlarged, the enlarged openings permitting the passage of water, e.g., wound exudate, the apertures when not enlarged preventing the wound from drying out, i.e., providing a moist environment.
U.S. Pat. No. 5,106,362 issued to Gilman in 1992 discloses a dressing comprising a base sheet for contacting the skin, the base sheet having an opening for placement over the wound and adhesive means for securing the base sheet to the skin; and vent means for providing controlled leakage of fluid along a path from the wound through the opening in the base sheet, the vent means comprising a cover means covering the opening, the cover means permitting the passage of the wound fluid therethrough while reducing evaporation through the opening and thereby helping to insure a moist environment while wound fluid is removed from the wound.
More recently, U.S. Pat. No. 5,308,313 issued to Karami et al. discloses a wound dressing comprising a thin conformable sheet material, a portion of which is adapted for placement over a wound and skin surrounding the wound, the surface of the sheet material adjacent the wound carrying a discontinuous layer of a pressure-sensitive adhesive, the discontinuous layer of adhesive having repeating areas containing no adhesive, at least a portion of only the repeating areas of the sheet material having no adhesive having slits extending through the opposed surfaces to permit transfer of wound fluid unimpeded by presence of adhesive material which can clog the slits, the dressing having an absorbing fabric disposed over the surface of the sheet material opposed from the surface containing the adhesive to provide a reservoir for receiving and retaining wound fluid diffusing to it through the slits; and a cover sheet over the absorbent layer, the cover sheet being air-permeable so that the wound can xe2x80x9cbreathexe2x80x9d, but being bacteria- and water-impermeable.
As will be discussed in detail hereinafter, the present invention is directed to a wound dressing consisting essentially of three layers of non-woven fabrics laid down sequentially to form the dressing. Accordingly, it is thought relevant to acknowledge in the discussion of the BACKGROUND OF THE INVENTION that the concept of providing a wound dressing comprising non-woven fibers is of course known in the art and, further, to mention illustrative patents describing non-woven material useful for this purpose.
U.S. Pat. No. 4,530,353 and a division thereof, U.S. Pat. No. 4,607,633 issued to Lauritzen are directed to the concept of providing low cost wound dressings of the so-called xe2x80x9cstripxe2x80x9d and xe2x80x9cislandxe2x80x9d adhesive bandage varieties. In Col. 2 of the ""353 earlier patent, it is mentioned that the bandages are conveniently prepared from a continuous web having a width equal to the overall length of the desired bandage plus twice the pad length to allow for the Z-fold construction of the patent. In Col. 3 it is stated that the bandage material contemplated by the patentee comprises a mixture of cellulose or other absorbent fibers and polyethylene or other heat-fusible fibers. The heat-fusible fibers are interspersed throughout the web and are preferably present in an amount of at least 10% by weight.
In Col. 4, examples of absorbent fibers to be employed in the practice of the invention include rayon staple fibers, cotton fibers, short length natural cellulosic fibers such as wood pulp fibers and cotton lintners, and mixtures thereof.
The non-woven fabrics described in the Lauritzen patents are further illustrative of the non-wovens that may be employed in the present invention.
The patents mentioned above represent but a cursory search of the art and accordingly are not intended to be indicative of the full state of the patent literature on the recited art. Nevertheless, they are believed to be fairly representative of the prior art to the present invention.
Suffice it to say that nothing in the aforementioned patent literature fully meets the criteria for a non-woven dressing capable of removing excess wound exudate from contact with the wound in a sterile atmosphere through a porous and patterned skin contact layer designed to materially reduce if not to prevent completely skin damage inherent in removal of the dressing, e.g. for replacement of the dressing and/or for inspection of the wound.
It is to this task to which the present invention is directed.
In accordance with the present invention, this task is solved in an elegant and cost-effective manner well suited for mass production on manufacturing assembly lines by providing a non-woven wound dressing comprising a non-woven fabric reservoir for receiving and retaining wound exudate sandwiched between what may be described as inner and outer layers of non-woven fabrics, the inner layer being adapted for placement to cover the wound, the outer layer providing an air- and vapor-permeable, but a bulk water- and bacteria-impermeable barrier for the dressing The inner layer has a plurality of spaced tapering elevations of the fabric or xe2x80x9cdimplesxe2x80x9d, the tapered ends of which are provided with a pressure-sensitive adhesive. These relatively small spaced deposits together define a discontinuous adhesive layer for adhering the dressing covering the wound.
For a detailed description of the invention and the advantages and improvements over the state of the art it provides, attention is invited to the following detailed description taken in conjunction with the accompanying drawing.